This invention relates generally to downhole motors used in drilling the bore of a subterranean well. More particularly, this invention relates to a new and improved flexible coupling used to interconnect and transmit movement between the rotor and drive shaft of a downhole motor.
Drill apparatus wherein a drill bit is operated by a downhole motor, such as positive displacement fluid motors or turbine driven motors, are well known in the prior art. In such motors, the drill bit is rotated by a rotor being turned by flow of fluid, such as drilling fluid through the motor assembly. A downhole motor of this type which utilizes a positive displacement Moineau motor is disclosed in U.S. Pat. No. 4,729,675 which is assigned to Teleco Oilfield Services, Inc., the assignee hereof. The downhole motor of U.S. Pat. No. 4,729,675 is commerically marketed under the trademark MAGNA-DRILL.
Downhole motors include a connecting rod which functions to transmit the motion from a rotor or turbine to a drive shaft. In the case of a positive displacement motor of the type disclosed in U.S. Pat. No. 4,729,675, the connecting rod must transmit and convert eccentric motion from the rotor to rotary motion of the drive shaft. This means that the connecting rod must compensate for angular misalignment between the rotor and drive shaft. In U.S. Pat. No. 4,729,675, this compensation is effected by a rod which includes opposed upper and lower universal joints. However, while suitable for its intended purposes, there is a continuing need for improved connecting rods capable of reliable high torque transmission between rotor and drive shaft for extended periods of time.